Britain’s regional accents are not only surviving but are tightening their grip, a series of academic studies has found.

Geordie, Scouse, Mancunian and Brummie inflections are becoming more distinct and dominant because they are one of the few remaining badges of identity against the homogenising effects of modernity.

Conventional wisdom was that accents would disappear and merge into a national way of speaking, albeit with some class and regional variations.

Now, however, experts are finding a far more subtle pattern. While big-city accents are surviving and even colonising surrounding areas, the nuances between districts within those cities are disappearing.

Outside the cities, the hundreds of accents that once distinguished small towns and rural districts are gradually being subsumed into regional “super-accents”.

Experts have identified 8-10 of these likely to predominate within the next 40 years. They range from estuary English, the glottal-stop-strewn argot of southeast England, to the burr of the southwest and separate accents in the West Midlands, Yorkshire and north and south Wales.

The resilience of urban accents, however, is one of the the most marked trends of recent years. It is most evident in northern England; in the south only two cities — London and Bristol — have strong accents of their own.

“People want to protect their identity,” said Dominic Watt, a lecturer in forensic speech science at York University. “You could be parachuted into pretty much any British city and the shops look the same, people dress the same and have similar pastimes and interests. What still makes these places separate and distinct is the dialect and accent.”

Liverpool is typical of a city with a distinctive accent that is thriving. Studies have found that some Scouse features, such as where the “k” sound is pronounced “kh” in words such as back, are becoming more prominent and widespread. The effect has even spread into north Wales.

Paul Kerswill, professor of sociolinguistics at Lancaster University, is about to begin a study into the spread of the Liverpudlian accent. “Liverpool and Manchester are only half an hour apart but the accents remain rock solid,” he said. “There must be a lot of commuting between the two cities but they are not merging.”

Kerswill said the Geordie accent was also resilient and that, like Scouse, it has established a wide area of influence from its Tyneside heartland to the west coast and as far north as Berwick-upon-Tweed. Clive Upton, professor of modern English language at Leeds University, added that there was no sign that children were speaking with weaker accents. “They are being passed down to a younger generation, who might have been expected to have watered them down but have not,” said Upton.

The survival of accents is also helped by their increased prominence on television.

Ant and Dec, the television presenters, still speak with a distinct Geordie accent despite moving from Tyneside to London. They have said that they made a conscious decision to retain their pronunciation.

Another famous Geordie, Cheryl Cole, has also found success, first in the pop group Girls Aloud and then by becoming a judge on The X Factor reality TV show, where she went on to mentor this year’s winner, Joe McElderry, also a Geordie.

Cole’s accent may have proved an advantage as the pair could effectively speak in code. “When me and Cheryl were having conversations in full Geordie, people would be, like, ‘It’s like a different language’,” McElderry said recently.

In addition to regional and city accents, researchers say that a north-south divide still persists in accents. Elements of southern speech are only rarely incorporated into northern accents and dialects.

“Northerners do not want to sound like southerners,” said Kerswill.

Accents are more varied in northern England because they have not been subjected to the mass levelling of speech caused by London and its commuting hinterland.

In the southeast, Kent, Essex and East and West Sussex are all losing their distinctive accents while the capital’s own cockney is also under threat.

The extent to which identity is equated with accent is shown in a study by Watt straddling the English-Scottish border. His researchers found that in Eyemouth, on the Scottish side of the border, locals clearly pronounce the letters “ar” in the word car. Nine miles away in Berwick, however, where a variant of Geordie is spoken, the same word is articulated as “caa”. In both towns people saw themselves as strongly Scottish and English respectively.